After a good boost on a B6-0, the C6-7 sustainer never did light, and  the rocket lawndarted near the creek.  As I approached and saw it in the bare dirt, I momentarily had hopes that the dirt might be soft, that the rocket might have escaped damage.

But it wasn't to be.  As described above, the nosecone had been partially swallowed, and the airframe accordioned.  My first thought was that, if I could find a suitable coupler, the fin can might be salvageable.  Otherwise, I'd be putting a whole new rocket under the nosecone.

While I didn't have a T30 coupler per sé, a spent 29mm single use Aerotech motor, with a couple wraps of tape, fits perfectly in the Quest T30 tubes. 

After leaving the rocket on the bench a few weeks, I finally took a closer look to see what might be salvaged.  The nosecone, being made of hard pine, had only minor damage and could be easily repaired with sanding and filler.

There were multiple issues with the airframe.  It needed to be cut off at the lower end of the accordion wrinkle.  However, the forward motor mount centering ring was not far below that point, and ideally, there needs to be ~1 caliber of coupler below the joint (and another caliber above).  This helps ensure that the replacement tube lines up perfectly with the original.

Another consideration was the launch lug.  If the cut line could be kept even with or just forward of the lug, then that would not need to be replaced.

The two previously broken fins were removed and replaced.  For the coupler, I sawed the ends off a spent Aerotech F23 and sanded its insides to remove all the residue.  A new forward tube was scavenged from my small stash of Quest parts.  I wasn't too concerned with getting it exactly the right length.  In fact, I was thinking that making the rocket a tad longer than scale might come in handy if another incident befalls it.

After applying a couple wraps of masking tape, the coupler and replacement aiframe were epoxied in place.  One really nice feature of epoxy is that it doesn't set real fast.  You have time to work things around and get the tubes perfectly aligned.

I set the rocket aside and returned to it a few days later.  With my dremel, I grinded down the seam and removed enough material so that once the area was filled, it would be flush; there would be no hump at the seam.

A piece of aircraft tissue paper was cut to cover the seam.  Regular strength Elmer's Fill-n-Finish was used to begin filling the seam.  Thinned FNF was applied to the tissue.  That in turn was applied over the seam and coated with more thinned FNF.  Basically, this method is a miniaturized version of tape-and-bedding drywall.  But instead of drywall mud and tape, I use FNF, tissue and thinned FNF.

After the seam treatment, I filled the fin roots and around the launch lug with FNF.  A wet finger works great to shape the FNF and minimize the amount of sanding needed later.

Looking down the tube, the coupler is visible.  The wet look around the coupler is due to the epoxy.  The wet appearance of the tube opening is caused by CA.  A few drops were applied and spread around with a Q-tip, then sanded smooth.  This prevents the opening from getting "fuzzy" due to the repeated insertions and extractions of the nosecone.  Plus it helps protect the tube against dings.
 

December 23, 2008